QCB board

QCB (Quad Card Backplane)

Quad Card Backplane for 3U eurocards. Splits USB 2.0 and 10/100M Ethernet (plus RS485 and an ID EEPROM) out to 4 eurocards.

Status: ready for prototype order

• Schematic and PCB routing are done (rev 0.1), production files generated.
• A full design review (schematic + PCB + EMC + SPICE) was completed on 2026-08-03 and re-checked since; see Documentation below.
• Fiducials added (2 per side, hand assembly), Y2 load caps C41/C42 now included in the BOM, datasheets for IP175G, FE1.1s and UT8413A in doc/datasheet/.

Production outputs: schematic PDF · PCB PDF · interactive BOM · gerbers

Architecture

The board is a backplane hub card built around two switching ICs, fanned out to 4 identical eurocard channels:

• U1 (FE1.1s) — 4-port USB 2.0 Hi-Speed hub, one port per channel.
• IC1 (IP175G) — 5-port 10/100 Ethernet switch. One port is broken out to an RJ45 (J3) via magnetics (H1102NL); the other 4 go to the channels.
• 4× channel (con1.kicad_sch, reused as CON1–CON4) — each with its own USB D+/D-, Ethernet TX/RX pairs, RS485±, ESD protection, and an identification EEPROM (M24C02) on its own I2C bus.
• pwr.kicad_sch — power input (Molex Mini-Fit connector J6), polyfuse, ferrite bead, ESD protection. No on-board regulator — +3.3V/+5V/+12V are supplied by the backplane.
• Channels land on 4 backplane connectors (DIN41612 2×32, J7–J10).

4-layer PCB (F.Cu / In1.Cu / In2.Cu / B.Cu), 101.6 × 128.7 mm.

Features

• 10/100 Ethernet switch with an external RJ45 port
• USB 2.0 Hi-Speed 4-port hub
• Per-channel RS485 and identification EEPROM
• 4× 3U 6TE eurocard, IEEE 1101.1-1998 format (128 × 30.1 mm)
• Powered entirely from the backplane (no on-board regulator)

Repository structure

pcb/        KiCad project (schematic, PCB, jobsets, 3D packages, datasheets cache)
doc/        Design review report, TODO list and component datasheets (tracked, human-readable)
media/      Renders/photos used in this README
prod/       Generated production outputs (gerbers/zip, BOM, schematic & PCB PDFs)
analysis/   Raw output of automated design-review tooling (gitignored, regenerable)

Documentation

• doc/DESIGN_REVIEW_2026-08-03.md — full schematic/PCB/EMC/SPICE design review
• doc/TODO.md — outstanding items before the board can be ordered

License and Contribution

MIT License

Open to contributions in both software and hardware!